Aliphatic tertiary amines are important intermediate products of fabric softeners, antistatic agents, additives for gasoline, shampoos, rinses, bactericides, detergents, etc., and have been used in extensive domestic and industrial application fields.
As the method for producing the aliphatic tertiary amines, there is known an amide reduction method in which an amide compound obtained from inexpensive regenerative fatty acids is used as a raw material. As the amide reduction method, there are conventionally known various methods using a copper/chromium-based catalyst, a noble metal-based catalyst, etc. For example, Patent document 1 discloses the method using a noble metal-based catalyst. However, the method described in Patent document 1 inevitably requires to use a solvent, resulting in problems such as poor productivity. In Patent Document 2, it has been attempted to enhance a dehydration efficiency and improve a reactivity by physically adding zeolite to a palladium/rhenium catalyst. However, the method described in Patent document 2 requires a high reaction pressure. Also, Patent Document 3 discloses the method using a copper/chromium-based catalyst. However, the method described in Patent document 3 also requires a high reaction pressure as well as a large burden of facilities. Patent Document 4 discloses the method of enhancing a durability of a copper/chromium-based catalyst by adding manganese thereto. However, the method described in Patent Document 4 also requires a high reaction pressure and flowing a large excess amount of hydrogen through the reaction system. Further, Patent Document 5 discloses the method of reducing an amide using a hydrogenation catalyst, in which a copper/chromium-based catalyst is mentioned as a preferred example of the hydrogenation catalyst. However, these catalysts used in the above conventional methods must be handled with great care to ensure a safety, etc., upon disposal. Therefore, there is a demand for development of chromium-free catalysts.
Patent Document 6 discloses the method using a chromium-free copper-based catalyst such as a copper/zinc catalyst, a copper/zinc/ruthenium catalyst and a copper/nickel/ruthenium catalyst. However, this method is still unsatisfactory in reaction selectivity.
Patent Document 1: JP 9-241222A
Patent Document 2: JP 63-255253A
Patent Document 3: DP 1493839A
Patent Document 4: U.S. Pat. No. 5,075,505
Patent Document 5: USP 2006-287556A
Patent Document 6: JP 2001-302596A